1. Field of the Invention
The present is related to a method and an apparatus for analyzing performance of a multi-stage radio frequency amplifier, and especially to a systematic method for rapidly analyzing stage gain and loss of each amplifier.
2. Description of Related Art
Radio frequency amplifiers are important in the design of radio frequency integrate circuits. When circuits are operated under microwave and radio frequencies, circuits with mismatched impedances suffer from decay and loss of power gain.
FIG. 1 shows a prior art single-stage radio frequency amplifier, which comprises an input power source circuit 010, an input-stage matching network 030, a single-stage amplifier 050, an output-stage matching network 070 and an output circuit 090. The input power source circuit 010 further includes an input source 012 and an input power source characteristic impedance 014; the impedance value of the input power source characteristic impedance 014 is 50 ohms.
The prior art method for analyzing the single-stage radio frequency amplifier is to find a reflection coefficient ΓS of a power source terminal, a reflection coefficient ΓL of the load, an input reflection coefficient ΓIN, and an output reflection coefficient ΓOUT. The four coefficients can be adjusted for acquiring preset gain value.
Matching methods in producing multi-stage radio integrate circuits are important issues in recent years. Prior art methods for analyzing power gain are designed for single-stage radio frequency amplifiers and microwave amplifiers; effective methods for analyzing power loss of multi-stage radio frequency amplifiers have not yet been successfully proposed. A common method applied for analyzing a multi-stage radio frequency amplifier is trial and error, but this wastes time and is ineffective. Prior art circuit simulation methods are hard to use in accounting for the reason why power gain decays.